Molecular sieving and adsorption of uremic toxins by a dual-layer hollow fiber mixed matrix membrane (DLHF

Abstract

A large amount of purified water is used in conventional hemodialysis (HD) for treating end-stage kidney disease (ESKD). To minimize the water demand and waste generation, the regeneration of dialysate is considered to be the most efficient control strategy. In this study, an innovative dual-layer hollow fiber (DLHF) mixed matrix membrane (MMM) incorporated with amine-functionalized mesoporous silica nanoparticles (MPS-NPs) was developed to regenerate spent dialysate. The fabricated DLHF-MMM configuration enabled the continuous removal of small, medium, and large weight uremic toxins (UTs) through dual mechanisms. The inner layer composed of polyethersulfone (PES) and polyethylene glycol (PEG) rejected large molecular weight UTs (i.e., MW > 500 Da) via the molecular sieving. Meanwhile, the outer layer containing amine-functionalized MPS-NPs effectively removed small weight UTs such as urea, creatinine, and hippuric acid. The DLHF-MMM with 6 wt% of amine-functionalized MPS-NPs demonstrated the most favorable characteristics, i.e., high water permeability (298.6 ± 3.2 mL/m2.h. mmHg) and adsorption capacity of urea (523.5 mg/g), creatinine (28.1 mg/g), and hippuric acid (3.1 mg/g). Notably, the optimal membrane (DLHF-4) also achieved favorable removal rates from the actual patient’s spent dialysate, i.e., urea (74.4%), creatinine (56%), hippuric acid (16.1%), and lysozyme (58.7%, additionally spiked as a mimicking for β-2 microglobulin). These results indicate that the fabricated DLHF-MMM in this study can effectively overcome the challenges posed by the complex matrix components. Overall, the results of this study demonstrate that the DLHF- MMM incorporated with amine-functionalized MPS-NPs is a promising potential tool for the regeneration of dialysate. Furthermore, this approach could potentially contribute to water conservation and reduce the burden on wastewater treatment processes associated with conventional HD wastewater. Keywords: Water consumption, amine-functionalized mesoporous silica nanoparticles, hemodialysis, spent dialysate, uremic toxins, dual-layer hollow fiber membrane